DUPLEX CRITERIA FOR GRADING INTERNAL CAROTID-ARTERY STENOSIS GREATER-THAN-50-PERCENT BASED ON MULTIREGRESSION ANALYSIS

Different opinions exist about grading >50% stenosis resulting from di fferences in angiographically estimated measurements and differences i n weighing hemodynamic parameters at duplex scanning. The aim of this study was to reevaluate the correlation between duplex scanning measur ements and angiographic findings in >50% stenosis by using correlation coefficients instead of earlier determination coefficients in multire gression analysis in prediction of an absolute percentage of stenosis greater than or equal to 50%. The authors correlated the angiographic findings for 58 vessels with 50%-99% stenosis with findings at duplex examination. Peak systolic velocity (PSV) >1.2 m/s was the limit for > 50% stenosis. The degree of stenosis was estimated as the smallest dia meter of the diseased vessel divided by normal diameter of the vessel at the same level. Predictive values of different variables either alo ne or in combination were calculated by means of multiregression analy sis. The highest predictive value was PSV, followed by late diastolic velocity (LDV) and pulse pressure (PSV - LDV) according to multiregres sion analysis. The results of Doppler evaluations of periorbital flow (POF) enhanced the differentiation between >75% stenosis and <75% sten osis. The combination of PSV and LDV and the result of POF coded as no rmal and abnormal had the highest accuracy in the prediction of absolu te percentage of stenosis with a difference of 6.3 +/- 4.3% (SD) betwe en the results of duplex scanning and angiography (r = 0.88). The accu racy in discriminating instances in which there was at least 75% reduc tion in luminal diameter was 98.2%. We found the quotient between PSV in the internal carotid artery and PSV in the common carotid artery to be less predictive with an accuracy of 84%. However, in the presence of severe stenosis in the external carotid artery, periorbital examina tion is not reliable. In such a situation it is preferable to use an e quation based on pulse pressure and LDV. In prediction of >50% stenosi s we found multiregression analysis in the assessment of the predictiv e value of combined variables to be more accurate than single regressi on of each variable.